The present invention relates to a planar inverted F-type antenna and more particularly to an improved planar inverted F-type antenna for increasing operative bandwidth and enhancing signal quality.
The rapid innovation and development of wireless communication technology have created a wide range of communication products in recent years. Among them, mobile communication products that integrate 3C technologies and communication modules are the mainstream of the market these days. These products include notebook computers, PDA, Palm, etc. They can couple with communication modules to link LAN (Local Area Network), to transmit and receive e-mail, and to receive instant information (such as news, stocks quotations and so on) for sharing resources and information. The planar inverted F-type antennas are known to have the advantages of compact size and light weight, thus have been widely adopted as built-in antennas in the mobile communication products.
Referring to FIG. 1 for a conventional planar inverted F-type antenna, the antenna includes a metal ground plane 10, a flat metal plate 12, a short circuit leg 14 and a feeding leg 16. The metal ground plane 10 is substantially parallel with the flat metal plate 12 and has a feeding metal bore 15. The short circuit leg 14 and the feeding leg 16 are located respectively on one side of the flat metal plate 12. The short circuit leg 14 connects the metal ground plane 10. The feeding leg 16 passes through the feeding metal bore 15 to connect a matching circuit (not shown in the drawing) for generating matching impedance. The flat metal plate 12 is a rectangular thin metal sheet having one side connected with the short circuit leg 14 to form a short circuit end and another side formed an open circuit end. The distance between the short circuit end and the open circuit end is preferably a quarter of wavelengths.
As the current on the flat metal plate 12 adopting conventional techniques has a constant length, the transmitting and receiving signals through the antenna also have constant frequency. As a result, the operative bandwidth is limited, and thus applications of the antenna are restricted.
Moreover, the feeding leg 16 adopting conventional technique is located at one side of the flat metal plate 12. Because the antenna is not a symmetrical structure, hence it cannot generate symmetrical radiation field in the horizontal direction. As a result, signal transmission and receiving quality of the antenna is definitely not satisfactory.
Therefore, producers of the planar inverted F-type antenna have devoted a lot of research and development efforts to improve the operating bandwidth and enhance the transmission quality.
The primary object of the invention is to provide an improved planar inverted F-type antenna for increasing operating bandwidth of the antenna.
Another object of the invention is to provide an improved planar inverted F-type antenna for enhancing signal quality of the antenna while transmitting and receiving data.
A further object of the invention is to provide an improved planar inverted F-type antenna design that is simpler to fabricate and is adaptable for mass production.
The improved planar inverted F-type antenna of the invention has a feeding leg of the antenna soldered to a center location of a flat metal plate that has two symmetrical sides thereof. A supplying current is fed at the center such that left and right symmetrical radiation fields can be generated from the antenna structure plate. As a result, signal quality for data transmitting and receiving of the present invention is better than that of an antenna adopting the conventional techniques. Moreover, the invention offers various shapes of the flat metal plate to change the feeding current route distance so as to increase operative bandwidth. In addition, the invention provides a novel fabrication method to make the feeding leg and forms an inverted U-shaped slit structure at a selected location in the center of the flat metal plate. The middle portion of the metal slit structure is bent downwards to form a feeding leg for passing through the feeding metal bore to replace soldering for making the feeding leg. The antenna thus can be integrally made of a single metal element and may be adaptable for mass production.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.